esbuild rules for Bazel

The esbuild rules runs the esbuild bundler tool with Bazel. esbuild is an extremely fast JavaScript bundler written in Go, its current benchmarks show it can be 320x faster that other bundlers

Installation

Add the @bazel/esbuild npm packages to your devDependencies in package.json.

npm install --save-dev @bazel/esbuild

or using yarn

yarn add -D @bazel/esbuild

The esbuild binary is fetched automatically for your platform and is exposed via Bazel toolchains. To do this, add the esbuild_repositories rule to your WORKSPACE. You'll need to point it to the repository created by npm_install or yarn_install where the @bazel/esbuild package is fetched. (Typically, this is npm). Set the npm_repository attribute to the name of that repository.

npm_install(
    name = "npm",
    # @bazel/esbuild is a dependency in this package.json
    package_json = "//:package.json",
    package_lock_json = "//:package-lock.json",
)

load("@build_bazel_rules_nodejs//toolchains/esbuild:esbuild_repositories.bzl", "esbuild_repositories")

esbuild_repositories(npm_repository = "npm")  # Note, npm is the default value for npm_repository

To avoid eagerly fetching all the npm dependencies, this load statement comes from the "Built-in" @build_bazel_rules_nodejs repository rather than from @npm. In rules_nodejs 5.0 we intend to fix this layering violation by having the whole esbuild support distributed independently of rules_nodejs, and not require any package to be installed from npm.

See the API docs for esbuild_repositories for ways to customize how Bazel downloads the esbuild package from npm. Alternatively, advanced users can override the download altogether by defining the esbuild repository earlier in your WORKSPACE file, so that the maybe inside esbuild_repositories is skipped.

Overview

The esbuild rule can take a JS or TS dependency tree and bundle it to a single file, or split across multiple files, outputting a directory.

load("@npm//@bazel/esbuild:index.bzl", "esbuild")
load("@npm//@bazel/typescript:index.bzl", "ts_project")

ts_project(
    name = "lib",
    srcs = ["a.ts"],
)

esbuild(
    name = "bundle",
    entry_point = "a.ts",
    deps = [":lib"],
)

The above will create three output files, bundle.js, bundle.js.map and bundle_metadata.json which contains the bundle metadata to aid in debugging and resoloution tracing.

To create a code split bundle, set splitting = True on the esbuild rule.

load("@npm//@bazel/esbuild:index.bzl", "esbuild")
load("@npm//@bazel/typescript:index.bzl", "ts_project")

ts_project(
    name = "lib",
    srcs = ["a.ts"],
    deps = [
        "@npm//foo",
    ],
)

esbuild(
    name = "bundle",
    entry_point = "a.ts",
    deps = [":lib"],
    splitting = True,
)

This will create an output directory containing all the code split chunks, along with their sourcemaps files

Rules

esbuild

Runs the esbuild bundler under Bazel

For further information about esbuild, see https://esbuild.github.io/

name

A unique name for this target.

args

A dict of extra arguments that are included in the call to esbuild, where the key is the argument name. Values are subject to $(location ...) expansion

args_json

Internal use only

config

Configuration file used for esbuild, from the esbuild_config macro. Note that options set in this file may get overwritten. See https://github.com/bazelbuild/rules_nodejs/tree/stable/packages/esbuild/test/plugins/BUILD.bazel for examples of using esbuild_config and plugins.

define

A dict of global identifier replacements. Values are subject to $(location ...) expansion. Example:

esbuild(
    name = "bundle",
    define = {
        "process.env.NODE_ENV": "production"
    },
)

See https://esbuild.github.io/api/#define for more details

deps

A list of direct dependencies that are required to build the bundle

entry_point

The bundle's entry point (e.g. your main.js or app.js or index.js)

This is a shortcut for the entry_points attribute with a single entry. Specify either this attribute or entry_point, but not both.

entry_points

The bundle's entry points (e.g. your main.js or app.js or index.js)

Specify either this attribute or entry_point, but not both.

external

A list of module names that are treated as external and not included in the resulting bundle

See https://esbuild.github.io/api/#external for more details

format

The output format of the bundle, defaults to iife when platform is browser and cjs when platform is node. If performing code splitting or multiple entry_points are specified, defaults to esm.

See https://esbuild.github.io/api/#format for more details

launcher

Internal use only

Link the workspace root to the bin_dir to support absolute requires like 'my_wksp/path/to/file'. If source files need to be required then they can be copied to the bin_dir with copy_to_bin.

max_threads

Sets the GOMAXPROCS variable to limit the number of threads that esbuild can run with. This can be useful if running many esbuild rule invocations in parallel, which has the potential to cause slowdown. For general use, leave this attribute unset.

minify

Minifies the bundle with the built in minification. Removes whitespace, shortens identifieres and uses equivalent but shorter syntax.

Sets all --minify-* flags

See https://esbuild.github.io/api/#minify for more details

node_context_data

Provides info about the build context, such as stamping.

By default it reads from the bazel command line, such as the --stamp argument. Use this to override values for this target, such as enabling or disabling stamping. You can use the node_context_data rule in @build_bazel_rules_nodejs//internal/node:context.bzl to create a NodeContextInfo.

output

Name of the output file when bundling

output_css

Declare a .css file will be output next to output bundle.

If your JS code contains import statements that import .css files, esbuild will place the content in a file next to the main output file, which you'll need to declare. If your output file is named 'foo.js', you should set this to 'foo.css'.

output_dir

If true, esbuild produces an output directory containing all output files

output_map

Name of the output source map when bundling

platform

The platform to bundle for.

See https://esbuild.github.io/api/#platform for more details

sourcemap

Defines where sourcemaps are output and how they are included in the bundle. By default, a separate .js.map file is generated and referenced by the bundle. If 'external', a separate .js.map file is generated but not referenced by the bundle. If 'inline', a sourcemap is generated and its contents are inlined into the bundle (and no external sourcemap file is created). If 'both', a sourcemap is inlined and a .js.map file is created.

See https://esbuild.github.io/api/#sourcemap for more details

sources_content

If False, omits the sourcesContent field from generated source maps

See https://esbuild.github.io/api/#sources-content for more details

splitting

If true, esbuild produces an output directory containing all the output files from code splitting for multiple entry points

See https://esbuild.github.io/api/#splitting and https://esbuild.github.io/api/#entry-points for more details

srcs

Source files to be made available to esbuild

target

Environment target (e.g. es2017, chrome58, firefox57, safari11, edge16, node10, esnext). Default es2015.

See https://esbuild.github.io/api/#target for more details


Macros and Functions

configure_esbuild_toolchain

Defines a toolchain for esbuild given the binary path and platform constraints

name

unique name for this toolchain, generally in the form "esbuild_platform_arch"

binary

label for the esbuild binary

exec_compatible_with

list of platform constraints


esbuild_config

Macro for an esbuild configuration file and its assoicated dependencies

name

Unique name for this rule

config_file

The configuration file / entrypoint

srcs

List of source files referenced by the configuration

deps

List of dependencies required for this configuration

kwargs

Any other common attributes


esbuild_repositories

Helper for fetching and setting up the esbuild versions and toolchains

This uses Bazel's downloader (via http_archive) to fetch the esbuild package from npm, separately from any npm_install/yarn_install in your WORKSPACE. To configure where the download is from, you make a file containing a rewrite rule like

rewrite (registry.nodejs.org)/(.*) artifactory.build.internal.net/artifactory/$1/$2

You can find some documentation on the rewrite patterns in the Bazel sources: UrlRewriterConfig.java

Then use the --experimental_downloader_config Bazel option to point to your file. For example if you created .bazel_downloader_config you might add to your .bazelrc file:

common --experimental_downloader_config=.bazel_downloader_config

name

currently unused

npm_repository

the name of the repository where the @bazel/esbuild package is installed by npm_install or yarn_install.